So i'll keep this brief: I have an old account from the beta, during this free weekend i verified and my account and characters still exist, I've never bought the basegame, and now i'm finally convinced to buy the game, but on steam. Is it possible?

I'm bringing this question because is different from the old: "I bought the basegame on the game site, but i would like to buy a dlc on steam."

I'm guessing it is possible, but looking at those old post forums makes me doubt.

Note: If you are wondering why i'm going through this mess, it's just because where i live, steam offers more payment methods.